The invention relates to an ejection unit for an injection molding machine comprising a movable and a stationary mold mounting plate and a carrier plate which can be anchored to one of the mold mounting plates, and on which is mounted an electric motor with which an ejector plate can be displaced by way of a drive output shaft.
DE 42 28 140 A1 discloses an ejection unit for injection molding machines, in which an electric motor is mounted on the movable mold mounting plate. That electric motor is in engagement by way of a spur gear transmission with a plurality of rotatable screwthreaded spindles projecting from the mold mounting plate. The ejector plate is displaceable by way of female screwthreads on the screwthreaded spindles.
The object of the present invention is to improve an ejection unit of the kind set forth in the opening part of this specification, such that better use is made of the electric motor.
In accordance with the invention that is achieved in that a drive wheel for a further subsidiary function of the injection molding machine, for example mold height adjustment, can be coupled to the drive output shaft.
Instead of the mold height adjustment, the electric motor of the ejection unit according to the invention could also be used to effect actuation of the core draw means or to implement another subsidiary function of the injection molding machine.
The drive wheels are advantageously in the form of a gear wheel or a belt pulley.
In accordance with the invention it is provided both that the drive wheel for the ejector plate is permanently non-rotatably coupled to the drive output shaft while the second drive wheel is selectively coupleable to the drive output shaft and also that the two drive wheels are alternately coupleable to the drive output shaft.
Coupling of the drive wheels is preferably effected electromagnetically or pneumatically.
An embodiment of the invention provides that the drive output shaft projects into an axially displaceable coupling tube which has an outer gear ring and is coupled to the drive output shaft by way of a spline-key connection or the like, that the two drive wheels each have an inner gear ring and that the outer gear ring of the coupling tube can be brought alternately into engagement with the gear ring of the one drive wheel or the other by axial displacement of the tube.
A further embodiment of the invention provides that the coupling tube is axially displaceable by means of a bracket which bears in face contact and in frictional engagement against the drive wheel for the subsidiary function when the gear ring of the coupling tube is in engagement with the drive wheel for the ejector plate.
Embodiments of the invention are described hereinafter with reference to the Figures of the accompanying drawings.